1. Field of the Invention
The present invention relates to a detecting apparatus and method for detecting information, such as characteristics, identification, concentration, and presence or absence, of a liquid object or sample, by using an electromagnetic wave. Particularly, the present invention relates to a detecting apparatus and method using an electromagnetic wave at a frequency or frequencies including at least a portion of a frequency range from 30 GHz to 30 THz. The electromagnetic wave including at least a component in the above frequency range is called a THz wave in this specification.
2. Description of Related Art
In recent years, techniques using a THz wave have been energetically researched and developed. In particular, photon energy of a THz wave is approximately equal to energies of molecular skeleton vibration and intermolecular action of material, and hence, techniques using a THz wave are employed in analysis of material that uses spectra, etc. obtained by the spectroscopic method.
In the above situation, “APPLIED PHYSICS LETTERS/Vol. 80, No. 1, 2002, p. 154” discloses a proposal in which a THz-wave transmission path is formed on a substrate, DNA water solution is dripped and dried on the transmission path, and analysis of the DNA is carried out by detecting a change in a THz-wave transmission property of the transmission path. The proposal uses the fact that a dielectric constant of single-stranded DNA for the THz wave differs from that of double-stranded DNA, and shows that single-stranded DNA and double-stranded DNA can be separately identified based on a difference in the THz-wave transmission property of the transmission path.
As stated above, when optical characteristics of material, such as an absorption coefficient, complex refractive index, and the like, are obtained by detecting a change in a transmission condition of a THz wave used, analysis, detection, identification, etc. of the material can be conducted. In the method of the above reference, however, no means is used for dripping a liquid sample onto the transmission path in an improved controllability, and accordingly it is typically not easy to accurately drip the sample on the transmission path. The dripped liquid sample is likely to flow and spread, so a location of the dripped sample on the transmission path and an interaction area between the THz wave and the sample are not easy to appropriately regulate.